How do you make a rectangular prism 2 cubes long 4 cubes wide 5 cubes high?

Answer 1

-- Start out with 40 identical cubes.

-- Take 8 of them. Place them on the table in 2 rows, 4 cubes in each row,

without any spaces between them.

-- Take four more groups of 8 cubes. On other places on the table, arrange

each group in 2 rows of 4 in each row, just like you did the first group.

-- Pile all five groups up on top of each other, neatly, in one pile of five layers.

Pile them carefully, so that all the sides of the pile are flat, straight, and smooth.

There should be no holes in the pile, and you should have no cubes left over.

The pile of five layers is the rectangular prism you want.